In recent years, development of the vehicle has been advanced to be driven with combustion energy of a fuel gas or with electrical energy produced by the electrochemical reaction of the fuel gas. A high-pressure tank used to store a fuel gas, such as natural gas or hydrogen, may be mounted on such a vehicle.
In order to increase the drivable distance of the vehicle, it is preferable to fill the high-pressure tank with the fuel gas at a higher fill pressure (e.g., 70 MPa). The improvement in strength of the high-pressure tank is required to fill the high-pressure fuel gas in the high-pressure tank. The known technology winds the fibers impregnated with a resin on the outer circumferential surface of a liner to form a reinforcement layer, in order to improve the strength of the high-pressure tank. More specifically, the known technology reinforces a body section in a substantially cylindrical shape forming the liner with a hoop layer, while reinforcing hemispherical dome sections connected with the respective ends of the body section in a continuous manner with helical layers (for example, Patent Literature 1). The hoop layer is used to ensure the strength mainly in the circumferential direction, and the helical layers are used to ensure the strength mainly in the longitudinal direction (in the axial direction).
Another known structure of the high-pressure tank has an outer fiber layer formed by high-angle winding (also called “high-angle helical winding”) outside the liner, instead of the hoop layer (for example, Patent Literature 2). The outer fiber layer is formed by high-angle winding, because the hoop winding causes the fibers to slip along the outer surface of the dome sections in the dome shape and thereby fails to wind the fibers on the outer surface of the dome sections and form the hoop layer.